Aqueous Deficient Dry Eye Disease
What Causes Aqueous Deficient Dry Eye Disease?
Aqueous Deficient Dry Eye is a form of dryness that occurs when your ocular system is not producing enough tears.
There are 2 types of tears that your eyes can produce, Reflex tears and Basal tears. Reflex tears occur as a response, or reflex, to an outside factor, such as a foreign body. Common foreign bodies that I see among my patients is dirt, an eyelash, a small piece of metal when grinding without eye protection, or even coal from the train. These produce immediate and excessive tearing as the ocular system does all that it can to flush this object out of your eye. While reflex tears serve an important role, they are not tears that play a role in Dry Eye Disease.
Basal tears are the tears that your body produces on a consistent basis to keep the front surfaces of the eye (the cornea and conjunctiva) lubricated and healthy. Without constant production of basal tears, your cornea would dry out and scar over, causing pain and a permanent loss of vision. Basal tears also contain anti-microbials, which kill the many microscopic organisms that constantly bombard the front surface of our eyes throughout the day. These tears are secreted from the lacrimal glands, which are located behind your brow.
As your tears evaporate, your lacrimal glands produce a steady supply of basal tears. At Peak, we can evaluate your tear production by taking a photo of and than measuring the height of tears that are resting on your lower eyelid between blinks. This is called the tear meniscus height (Figure 1). However, inflammation of the lacrimal glands can cause of decrease in basal tear production. The most severe form of this occurs in Sjogren’s Syndrome patients, where your immune system attacks the glands that produce tears and saliva. Most patients with Aqueous Deficient Dry Eye do not have Sjogren’s Syndrome, but rather have general, less severe inflammation of their lacrimal glands, which decrease the amount of basal tears that they produce. This leads to irritated, red, gritty-feeling eyes. If left untreated, the cornea can become more and more damaged, eventually leading to permanent scarring.
Aqueous Deficient Dry Eye Disease Mild/Moderate Treatments
If there is substantial damage, like what is seen in Figure 2 above, then I will likely prescribe a short course of a mild steroid eyedrop to quickly reduce the inflammation on your ocular surface, thus allowing your eye to heal properly. Steroids are very beneficial and safe for short term use, but do have potential complications if used long term, so we will transition to dry eye prescription eye drops that are safe for long term use, of which we have a few options. The first prescription drop to be FDA approved for the treatment of dry eye disease was Restasis in 2003. The benefit with this drop is it tends to be the cheapest and most widely covered under medical insurance plans, the negative being that we do not expect you to notice any improvement until 3 months after starting the drop. The next drug to be FDA approved for the treatment of Dry Eye Disease is Xiidra, with the benefit being it only takes 6 weeks to have an effect, but does come with a metallic taste in the back of your throat when you instill the drop for the first few days. Cequa is another option, which also has a shorter time to improvement (1-2 months), but is hard to get covered by insurance as it is so new.
Severe Aqueous Deficient Dry Eye Disease Treatments
In some cases, the cornea is so damaged that those treatments are not enough. If your cornea is severely damaged, you are at risk for infection or scarring, which can lead to permanent vision loss if not improved quickly.
One of the most effective treatments for severe corneal damage from dryness is an amniotic membrane. At Peak Eyecare, we typically use Prokera membranes made by Bio Tissue (Figure 3). These membranes are harvested for this specific purpose, and will aid in healing your cornea when placed on your eye for 1 week. In most cases your medical insurance will cover this treatment. These membrane are typically very well tolerated. The negatives for treatment with amniotic membranes is that we can only treat one eye at a time, as it will substantially reduce your vision during the week that it is in place, and it is slightly uncomfortable at first.
If the damage seems to be lingering and is not improving with the above treatments, another option we will consider is autologous serum eye drops. These drops are made from the plasma of your own blood, and thus has a much more targeted affect on decreasing the inflammation on your ocular surface and promotes healing of your cornea. To make these drops, your blood is drawn, then centrifuged to separate the serum from the rest of the blood. This serum is harvested and put into eye drop bottles to be used daily. While very effective, this process is not cheap, so I only recommend it when necessary.
Historically, eye doctors would treat Aqueous Deficient Dry Eye with punctal plugs. You have 2 puncta on each eye that drain your tears, one in the upper eye lid and one on the lower eyelid. They are located on the nasal side of each lid, and they drain tears to the back of your Nose and throat. This is why when you cry, you nose starts to run. The thought behind blocking the puncta with a plug was that if a patient is not producing enough tears, we can block the drain, thus keeping the eyes more lubricated. However, as we just discussed, the major cause of Aqueous Deficient Dry Eye is inflammation, so if we block the drain of the eye, we are keeping the inflammatory factors on the ocular surface, thus making the inflammation worse. An analogy would be dirty water in a sink. We would not want to plug the drain of the sink if our goal is to remove the dirty water.
That being said, there are rare cases when I will recommend and install temporary punctal plugs, always in combination with some of the above treatments. Examples would be severe Sjogrens Syndrome, or a condition called Neurotrophic Corneal Ulcer, found most commonly in uncontrolled diabetic patients. For these patients, we must use everything at our disposal to keep the eye lubricated and protect the eye from permanent scarring that could lead to blindness.
However, most cases of dry eye disease are not strictly Aqueous Deficient Dry Eye Disease, but rather a combination both Evaporative Dry Eye Disease and Aqueous Deficient Dry Eye Disease. Consequently, we almost always combine different treatment to effectively treat your dryness. If you eyes are bothering you, we would love to help, and promise to do all we can for as long as we need to in order to improve your eye comfort.